This invention relates to a mode switching mechanism for a recording and/or reproducing apparatus for recording and/or reproducing information signals on or from a tape, such as a magnetic tape, as the recording medium.
In connection with such a recording and/or reproducing apparatus there is so far proposed a so-called reversible tape apparatus in which recording and/or reproduction is performed with the tape being selectively run in either the forward direction or the reverse direction.
A variety of types of such recording and/or reproducing apparatus are also proposed, in which predetermined cam surfaces are formed on a planar surface of a cam gear for selectively switching various operational modes, such as a forward (FWD) mode in which the recording tape is run in the forward direction for recording and/or reproduction, a reverse (REV) mode in which the magnetic tape is run in the reverse direction for recording and/or reproduction, a fast feed (FF) mode, a rewind (REW) mode or a stop (STOP) mode.
Such a recording and/or reproducing apparatus is so constructed that a mode switching mechanism for switching the various operational modes is actuated by a cam surface on rotation of the cam gear. The angular rotational positions of the cam gear are associated with the various operational modes. Thus a predetermined operational mode can be selected by rotating the cam gear by an electric motor and halting and positioning the cam gear at predetermined angular positions.
For example, the reversible type recording and/or reproducing apparatus which is provided with a mode switching mechanism, as proposed in our copending Japanese Patent Application No. 62-163353(1987), is so constructed that a pair of capstans for running the tape towards the forward or reverse side at constant speeds, a pair of reel shafts fitted with tape reels for taking up the tape and a sole cam gear for selectively switching a plurality of operational modes, are rotated by a sole driving motor. The apparatus is, in effect, what is called a one motor type tape recorder. With such a one-motor tape recorder, the drive power of the drive motor is transmitted to the capstans and reel shaft or the like by means of a drive power transmitting mechanism inclusive of drive belts or gears.
The cam gear has a peripheral gear formed with interrupted portions, and has cam surfaces and retained portions on its planar surface. This cam gear is positioned by the retained portion being retained by a cam gear retainer at a position in which the drive gear transmitting the drive power of the drive motor faces an associated one of the interrupted portions. The cam gear retention member is reciprocated between the retained position or the released position by means of a plunger and a biasing spring.
On rotation of the cam gear, the mode switching mechanism for switching the operational modes by the cam surface comes into operation. This mode switching mechanism switches the transmission route of the drive power by shifting the gear transmitting the drive power of the drive motor, and selects the desired operational mode by switching the direction of constant speed running of the tape by the selective abutment of the pinch roll against the capstans.
More specifically, for switching the operational modes in the above described recording and/or reproducing apparatus, the plunger is actuated to shift the cam gear retention member to release the retention of the cam gear, while the cam gear is rotated by a biasing member by way of initial triggering for engaging the drive gear with the gear section to rotate the cam gear. This actuates the mode switching mechanism to switch the tape running direction. This mode switching mechanism is actuated responsive to the angular position of rotation of the cam gear to effect switching to the desired operational mode associated with the angular position of rotation. Hence, the operation of the plunger is released when switching to the desired operational mode has been made, and the cam gear is again retained and positioned by the cam gear retention member for establishing the desired operational mode.
With the above described one-motor type recording and/or reproducing apparatus, the capstan pair and the reel shaft are rotationally driven by one and the same driving motor. The result is that the rotational load applied by the tape to the reel shaft is transmitted to the capstans so that the rotational speed of the capstans can be maintained at a high accuracy only with difficulty and so-called wow and flutter is produced to render it difficult to maintain satisfactory recording and/or reproducing characteristics.
With the above recording and/or reproducing apparatus, it is necessary to switch the torque or speed of rotation of the reel shaft between the recording and/or reproducing (forward or reverse) modes and the fast feed or rewind modes. This complicates the arrangement because a plurality of drive power transmitting mechanisms need be provided to provide for different speeds or rotational torques of the drive motor to the reel shaft with the use of what is called a torque limiting mechanism.
With a two-motor tape recorder in which the capstans and the reel shaft are rotationally driven by a separate dedicated capstan motor and a reel motor, respectively, it becomes possible to maintain the rotational speed of the capstans at a high accuracy to suppress wow and flutter. The drive power transmitting mechanism to the reel shaft can also be simplified by commuting the amounts of currents to the reel motor for switching the rotational speed of the reel shaft or the rotational torque between the recording and/or reproducing mode and the fast feed or rewind mode.
However, with the use of two driving motors, three separate driving means, that is these two driving motors and a plunger, are necessitated, thus complicating the arrangement and the assembling process, while elevating the costs.